Polychloroprene was the first synthetic elastomer used in rubber-based adhesives. It is still the most commonly used elastomer in a variety of adhesive compositions because of its ability to achieve rapid bond strength development with good tack or auto-adhesion, and because of its resistance to degradation by oils, chemicals, heat, sunlight and ozone.
In particular, conventional bonding adhesives used to adhere single-ply roofing membranes to various substrates generally utilize a polychloroprene polymer or a blend of different polychloroprene polymers as the sole elastomeric ingredient. Polychloroprene-based adhesives, despite certain disadvantages, are used extensively in the roofing industry because of their excellent initial bond strength and resistance to creep. Specifically, polychloroprene adhesives impart relatively low peel values and are susceptible to damage and loss of bond strength from extensive wet and dry cycles.
In a typical roof top environment there is a chance that the adhesive used for bonding roofing membranes to a roof substrate will be inadvertently exposed to moisture. Cuts in EPDM membrane, improper seam fabrication, and loose perimeter attachments of membrane to parapets are some sources of intrusion of moisture under the membrane. Typically, polychloroprene can withstand these moisture intrusions, but if allowed to be exposed to repeated wetting and drying conditions, polychloroprene adhesives will begin to lose their bond strength to the EPDM membrane and eventually separate therefrom.
Butyl rubber-based adhesive compositions have been used in connection with membrane roofing materials such as EPDM and neoprene for forming solid tapes or flowable adhesives which are used for sealing the joints between overlapping edges of roofing membranes. Butyl rubbers are known to impart high adhesion values and to be resistant to degradation upon exposure to moisture. Butyl rubbers, however, have not generally been used in flowable adhesive formulations for bonding roofing members to roof substrates, presumably because of their lower initial bond strength and because of their lower resistance to creep, as compared to polychloroprenes.